The present inventors found that quinoline and naphthalene derivatives have herbicidal activities and disclosed specific examples in Japanese Unexamined Patent Publication No. 56469/1990. Further, Japanese Unexamined Patent Publication No. 121973/1990 discloses that aromatic carboxylic acid derivatives containing quinoline, naphthalene, benzofuran, thiophene or pyridine ring have herbicidal activities.
However, the above-mentioned publications disclose nothing about specific compounds relating to the condensed heterocyclic derivatives of the present invention. Further, these compounds are not necessarily satisfactory from the viewpoint of the herbicidal effects. A number of other herbicides have been developed and contributed to the saving of energy for agricultural operations and to the improvement of the productivity. However, in their practical use, such herbicides also have various problems with respect to the herbicidal effects and the safety to crop plants.
The present inventors have conducted an extensive research on condensed heterocyclic derivatives with an object to develop a compound which is excellent in the herbicidal activities without bringing about phytotoxicity to crop plants. As a result, it has been found that the compounds of the present invention which are pyrimidine or triazine derivatives bonded to a condensed heterocyclic ring exhibit excellent herbicidal activities against not only annual weeds but also perennial gramineous weeds, cyperaceous weeds and broad leaf weeds in the paddy field treatment, upland soil treatment and foliage treatment, and they are highly safe to crop plants. The present invention has been accomplished on the basis of this discovery.